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CP521/621
CP521/621 — Installment Agreement Reminder Notice
What this IRS notice code means, and what to check before you reply.
What to do next
Start with these steps before you reply.
CP521/621
Read the notice carefully and note any deadline. Gather returns, notices, and payment records. Book a free strategy session before responding if the amount is large, unclear, or collection language appears.
What the IRS language says
Installment Agreement Reminder Notice
What it usually means
CP521/621 is in our IR Manual catalog. Official wording is dense — we translate it for business owners and individuals and map realistic next steps.
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